Carpets, for example continuous-sheeting product or carpet tiles, are manufactured by forming the carpet pile from tufts inserted, for example in the form of loops, into a woven or non-woven primary backing. In tufted carpet, the sheetlike primary backing holds the loops but loosely. Needlefelt carpets are manufactured by needling the tufts. In woven carpets, the tufts are interwoven with the primary backing.
To improve the attachment of the carpet pile to the sheetlike primary backing, a binder is applied to the reverse side of the primary backing. Aqueous types of polymer dispersions filled with fillers, for example chalk, may contain further additives such as thickeners and are generally precoated as a foam or in the unfoamed state.
It is particularly for the purpose of improving the dimensional stability of carpets that they are provided a further, secondary backing. The secondary backing generally comprises a woven fabric in a manufactured fiber such as polypropylene or in a natural fiber such as jute. The secondary backing is attached to the as-precoated carpet by further applying a binder. Again, aqueous types of polymer dispersions filled with fillers, for example chalk, may contain further additives such as thickeners and are generally applied as a foam or in the unfoamed state to form a secondary coating.
WO 90/00967 A1 describes the use of aqueous dispersions of vinyl acetate-ethylene copolymers or of styrene-butadiene copolymers or of styrene-acrylate copolymers instead of PVC plastisol as binders in carpet manufacture.
U.S. Pat. No. 3,779,799 describes a tufted carpet precoated with a binder composition where the binder is a vinyl acetate-ethylene copolymer dispersion (VAE copolymer dispersion) or a polyethylene dispersion or a dispersion of a carboxylated styrene-butadiene copolymer.
U.S. Pat. No. 5,026,765 describes a carpet coating composition comprising a vinyl acetate-ethylene copolymer dispersion wherein the copolymer further contains monomer units whose homopolymers have a Tg of at least 50° C.
U.K. patent GB 1,298,155 describes carpet coating compositions comprising a crosslinkable binder based on an aqueous mixture of vinyl acetate-ethylene copolymer, polyvinyl alcohol (PVOH) and glyoxal.
WO 2010/089142 A1 discloses a vinyl acetate-ethylene copolymer dispersion employed as a binder in carpet manufacture. The copolymer contains just 1 to 4 wt % of ethylene and is emulsifier stabilized only, although small amounts of protective colloid may be co-used for stabilization if necessary.
To improve adherence to polyvinyl butyral sheeting (as secondary backing), WO 2006/007157 A1 proposes employing a vinyl acetate-ethylene copolymer further comprising from 1 to 10 wt % of comonomer units containing functional groups such as carboxyl, amide, N-methylol or hydroxyalkyl groups. The copolymer is prepared by employing a mixture of emulsifier and from 0.05 to 4 wt % of protective colloid.
U.S. Pat. No. 6,359,076 proposes improving the water resistance of carpet coatings by employing crosslinkable vinyl acetate-ethylene copolymers which include OH-functional monomer units in combination with a crosslinker.
WO 2011/139267 A1 and WO 2011/140065 A2 propose improving the quality of carpet coatings based on vinyl acetate-ethylene copolymers by eschewing stabilization with protective colloid, emulsifier stabilizing only and copolymerizing functional crosslinkable comonomers such as silane-functional or multifunctional comonomers.
WO 2012/020319 A2 or WO 2012/020321 A2 discloses carpets notable for low flammability or good washability. The binder used was a vinyl acetate-ethylene copolymer dispersion having an average particle size dw of 50 to 500 nm, prepared by emulsifier stabilization, although up to 3% of protective colloid may additionally be used as a costabilizer if necessary.
WO 2013/093547 A2 relates to a carpet binder having an optimized composition for formulations with carbon black as a filler. The binder comprises a vinyl acetate-ethylene copolymer dispersion stabilized with emulsifier and cellulose ether.
WO 2013/123210 A1 relates to carpets manufactured by employing a binder mixture formed from a vinyl acetate-ethylene copolymer dispersion and from a styrene-butadiene copolymer dispersion. A proposal to improve the compatibility of the two different polymer dispersions involves eschewing polyvinyl alcohol in the VAE dispersion, and at most employing up to 1.5 wt % of polyvinyl alcohol, based on comonomers, as a protective colloid in the preparation thereof.
WO 2014/031579 A2 relates to a carpet coating composition which by way of binders may include inter alia a VAE dispersion which is emulsifier stabilized and may additionally contain up to 1.5 wt % of polyvinyl alcohol as a costabilizer if necessary. This dispersion is blended with an alpha-olefin-carboxylic acid copolymer and a crosslinker.
WO 99/10396 A1 proposes improving the rheology of VAE dispersions having a high solids content of at least 65 wt % by preparing them in the presence of a stabilizer mixture formed of more than 3 wt %, preferably 4 to 5 wt % of low molecular weight polyvinyl alcohol and 1 to 4 wt % of a nonionic emulsifier having a defined HLB.
WO 2013/001379 A2 describes polyvinyl alcohol-stabilized VAE dispersions. To optimize their viscosity, the stabilizing polyvinyl alcohol used comprises a mixture of 0.5 to 3 wt % of fully hydrolyzed polyvinyl alcohol and 1.5 to 4 wt % of partially hydrolyzed polyvinyl alcohol.
U.S. Pat. No. 4,921,898 relates to aqueous adhesive compositions based on a vinyl acetate-ethylene copolymer dispersion prepared in the presence of a stabilizer combination of 2 to 4 wt % of a low molecular weight polyvinyl alcohol with 2 to 4 wt % of an emulsifier. The adhesive composition is notable for rapid setting.
U.S. Pat. No. 4,239,563 describes aqueous vinyl acetate-ethylene copolymer dispersions useful as binders for consolidating carpets. The lower emission of volatile organic compounds (VOCs) versus styrene-butadiene latices is emphasized. The VAE dispersion is prepared via emulsion polymerization by use of emulsifier and/or protective colloid (inter alia polyvinyl alcohol). The VAE copolymer has a high ethylene content of 30 to 80 wt %, based on total comonomers.
U.S. Pat. No. 4,735,986 by way of prior art for carpet binders describes a composition comprising a vinyl acetate-ethylene copolymer dispersion stabilized with 5 wt % of polyvinyl alcohol, wherein the polyvinyl alcohol fraction comprises a mixture of a low-viscosity partially hydrolyzed PVOH and a medium-viscosity partially hydrolyzed PVOH. Disadvantages are stated to be an insufficient level of filler compatibility, the lack of compatibility with chalks of differing specification and the low compatibility with styrene-butadiene copolymer dispersions. The property profile is said to be improved on polymerizing in the presence of a stabilizer mixture of partially hydrolyzed PVOH, fully hydrolyzed PVOH and a nonionic polyalkoxylated emulsifier.
The disadvantage with the solely polyvinyl alcohol-stabilized vinyl acetate-ethylene copolymer dispersions hitherto used as binders in carpet coating compositions is their inadequacy in filler compatibility, for example with chalk, in highly filled formulations. True, the co-use of emulsifiers during the polymerization or the subsequent admixture of emulsifiers does improve the filler compatibility of an aqueous vinyl acetate-ethylene copolymer dispersion, yet the admixture of emulsifiers also degrades the mechanical properties of the coating obtained therewith.